Stir together cream cheese and Cheddar cheese; divide in half. Stir pesto into 1 half; stir onion, mustard and 2 or 3 drops pepper sauce into other half. Cover each half; refrigerate about 4 hours or until firm enough to shape.
Place cheese mixtures on cookie sheet. Shape each half into cone shape to look like a pine tree.
If desired, wrap each tree, label and freeze up to 1 month. Twelve hours before serving, remove trees from freezer. Thaw in wrapper in refrigerator.
Just before serving, roll trees in parsley, pressing it evenly onto trees. Press pine nuts onto trees in string form for garland. Press bell pepper pieces onto trees for ornaments. Top each tree with star shape cut from lemon peel. Serve with crackers.